Long time lurker here. Nobody ever asked a question about something I know about. I'm just here to learn.
I was a plasterer earlier in my career. You have recieved some good advice here. Scrape the loose skim coat until it sound. You can use durabond. If you are tempted to use real plaster use...
I used to move my unit from the truck to the garage. When i got a new truck the xm was included in the in dash radio. I am too cheap to pay for two subscriptions. I added the Internet radio option for $4 a month and got the app for my cell phone.
The cell phone connects to my dewalt boom box...